Red Simpson, an architect of the Bakersfield Sound with contemporaries Merle Haggard and Buck Owens and a champion of truck drivers, has died after suffering a heart attack in December. He was 81.

Of all the subgenres of country music, the truck-driving songs might be the most unique, as they romanticized a hard life spent on the highway, evading Smokey and his radar and popping pills to stay awake. Along with Dave Dudley, Red Sovine and C.W. McCall, Simpson gave truckers a voice. His biggest hit was 1971’s “(Hello) I’m a Truck” and also charted in the Top 40 with “Roll Truck Roll” and “The Highway Patrol.”

But Simpson was even more influential in creating the Bakersfield Sound, the California-born style of Telecaster-heavy twang that became associated with Haggard, Owens and their acolytes, from the Grateful Dead to Dwight Yoakam.

“He played a huge part in the Bakersfield sound and was a dear friend of mine for over 50 years,” Haggard wrote on Facebook, pointing out that Simpson had played on Haggard’s signature hit “Okie From Muskogee.”

Simpson continued to perform throughout his life and was on a tour of the Pacific Northwest when he had a heart attack. While recovering at home, he experienced distress on Friday, January 8th, and was rushed to a Bakersfield hospital where he died.

A recent exhibit on the Bakersfield Sound at Nashville’s Country Music Hall of Fame focused heavily on Simpson. He headlined the exhibit’s opening concert in March 2012.